Defined Benefit Plan, Change in Obligations and Fair Value (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Defined Benefit Plan, Fair Value of Plan Assets		$ 3,025	[1]	$ 3,223	[2]
Defined Benefit Plan, Funded Percentage	[3]	106.00%		105.00%
Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation	[3]	$ 2,716	[4]	$ 2,935	[4]	$ 2,575
Defined Benefit Plan, Service Cost	[5]	5	[3]	5	[3]	5
Defined Benefit Plan, Interest Cost	[5]	116	[3]	124	[3]	113
Defined Benefit Plan, Contributions by Plan Participants	[3]	0		0
Defined Benefit Plan, Actuarial Gain (Loss)	[3]	(171)		401
Defined Benefit Plan, Benefits Paid	[3]	(164)		(165)
Defined Contribution Plan, Administrative Expenses	[3]	(5)		(5)
Defined Benefit Plan, Fair Value of Plan Assets	[3]	2,879	[6]	3,080	[6]	2,873
Defined Benefit Plan, Actual Return on Plan Assets	[3]	(37)		371
Defined Benefit Plan, Contributions by Employer	[3]	5		6
Defined Benefit Plan, Funded Status of Plan	[3],[7],[8]	163		145
Defined Benefit Plan, Accumulated Benefit Obligation	[3]	2,716		2,935
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Benefit Obligation		65	[4]	69	[4]	81
Defined Benefit Plan, Service Cost		0		0		0
Defined Benefit Plan, Interest Cost		2		3		6
Defined Benefit Plan, Contributions by Plan Participants		6		11
Defined Benefit Plan, Actuarial Gain (Loss)		(2)		(10)
Defined Benefit Plan, Benefits Paid		(10)		(16)
Defined Contribution Plan, Administrative Expenses		0		0
Defined Benefit Plan, Fair Value of Plan Assets		156	[6]	160	[6]	$ 158
Defined Benefit Plan, Actual Return on Plan Assets		1		8
Defined Benefit Plan, Contributions by Employer		0		0
Defined Benefit Plan, Funded Status of Plan	[7],[8]	91		91
Fair Value, Disclosure Item Amounts [Domain] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Contributions by Plan Participants		$ 5		11
Defined Benefit Plan, Benefits Paid				$ (17)

[1] Fair value measurements do not include pension benefits accrued income amounting to less than 0.4% of total plan assets.

[2] Fair value measurements do not include pension benefits accrued income amounting to less than 0.6% of total plan assets.

[3] Employer contributions represent the benefits that were paid to nonqualified plan participants. Unfunded nonqualified supplemental pension plans are not funded through plan assets.

[4] Includes $81 million and $85 million of benefit obligations for the unfunded nonqualified supplemental pension plans at December 31, 2015 and 2014, respectively.

[5] Administrative fees are recognized in service cost for each of the periods presented.

[6] Includes $1 million of the Company's common stock acquired by the asset manager and held as part of the equity portfolio for pension benefits at both December 31, 2015 and 2014. During 2015 and 2014, there was no SunTrust common stock held in the other postretirement benefit plans.

[7] Other postretirement benefits recorded in the Consolidated Balance Sheets included other assets of $91 million at both December 31, 2015 and 2014.

[8] Pension benefits recorded in the Consolidated Balance Sheets included other assets of $244 million and $230 million, and other liabilities of $81 million and $85 million, at December 31, 2015 and 2014, respectively.